Process of producing acetaldehyde



Patented July 26, 1927.

UNITED STATES PATENT OFFICE.

I'm, A CORPORATION OF NEW JERSEY.

PROCESS OF PRODUCING ACETALDEHYDE.

Io Drawing.

This invention relates to improvements in catalysts, particularly to catalysts w h1ch are capable of causing oxidation reactions and to processes of oxidation wherein such catalysts are employed. It relates more specifically to the selective oxidatlon of ethyl alcohol and has particular reference to production of acetaldehyde by sub ecting ethyl alcohol to oxidation by means of oxygen either alone or admixed with other gases in the presence of a catalyst;

I am aware that the vapor phase catalytic oxidation of ethyl alcohol to acetaldehyde has been decribed before, but the following discloure of my invention will make clear the improvements which I have effected in the catalyst and also. in the-procedure over the previous processes.

The following equations are Involved in the vapor phase catalytic oxidation of ethyl alcohol:

It is obvious that equation-(l) represents the. desired course of the oxidatlonas all the succeeding equations represent either a loss of ethyl alcohol or acetaldehyde. Equations (1), (2) and (3) depend to the greatest extent on the inherent properties peculiar to any one catalyst while equatlons (4) and (5) really depend to greatest extent on the temperature of the catalyst or reaction zone during the oxidation. It is apparent that the temperature of oxidation should be as low as possible as equations (4) i and (5) represent pyrogenetic-reactions.

In the Journal fiir pracktische Ghemie, 5 year 1907 (N. S.) volume 75, pages 149 to 150, a process is vaguely described in which a mixture of ethyl alcohol vapor and a very small amount of air is p'assed throu h a combustion tube containing a layer 0 asbestos impregnated with vanadium pentoxide which is gently heated. at the start of the run. The heat of the reaction of the oxidation of the ethyl alcohol is said to soon cause the catalyst to glow, and continues to Application illed larch 18, 1922. Serial Ho. 548,483.

do so as long as the ethyl alcohol air mix- I ture is passed over it. No information is given in this article concerning the compo sition. of the air alcohol mixture, the amount of catalyst, the time of contact of the reaction mixture with the catalyst, the temperature of the catalyst,'various featuresof the apparatus, nor are the yields of acetaldchyde or acetic acid or the per ntage of unaltered alcohol or the composition of the exit gases given or their extent intimated, but judging by the much more carefully regulated experiments which I have made w1th vanadium oxide, the aldehyde yield as obtained by this above procedure was undoubtro rim Banana 00!- v edly quite low, and the yield of acetic acid and the amounts of decomposition and oxidation of the-ethyl alcohol hyde state were undoubtedl igh owing to the extremely high temperature ovf'the catalyst and reactionzone.

Another process described for the production of acetaldehyde is that of J. E..Orlofi',

beyond the aldey in the Journal of the Russian Chemical Society, volume 40, pages 203-'-215, year 1908.

According to the description, 3, mixture of 1.8 parts of air and 1.0 part of ethyl alcohol by weight is passed through a glowing freshly reduced copper gauze; A production of 63 pounds of acetaldehyde I of ethyl alcohol passed through the s stem was obtained with practically all of t e remaining alcohol undergoing further oxidation or decomposition into carbon dioxide water, carbon monoxide, ethyleneand asmall amount of acetic acid. From the above it is evident that about one-third of the alcohol passed through the catalyst is wasted. Orthat side by: side with the exothermic reaction of the oxidation of ethyl alcohol to acetaldehyde, there is an end0-' thermic reaction due to the decomposition of the ethyl alcohol into water and. ethylene,

caused by the extremely high temperature of the reaction zone, the reaction being CH CH OH=CH OH +H O.

Furthermore, the high catalyst temperature also causes a pyrogenetic decomposition of the acetaldehyde, producing thereby methane and carbon monoxide. twodisadvantageous side reactions occur in per. 100 pounds That these Orloffs process isevidenced by the fact that a very large amount of ethylene, methane and carbon monoxide was found in the exit ases. Experimental evidence also exists s owing that these two reactions ensue, as W. Ipatiew in the Berichte der deutschen Chemischen Gesellschaft, volume 34, pages *methane and carbon monoxide resulting 3 heat of alcohol and t from the pyrogenetic decomposition of a part of the acetaldehyde which is formed to a small degree. Furthermore, W. A. Bone and H. L. Smith have shown in the Journal of the Chemical Society Transactions, volume 87 (year 1905) pages 913 to 916, that acetalde yde, when subjected to a temperature of 400 C'. in a glazed porcelain tube, undergoes very rapid and almost complete decomposition into equal quantities of methane and carbon monoxide, while at 600 C. the decomposition is more severe, there bein formed some carbon and hydrogen in a dition to the methane and carbon monoxide.

,In both of the above mentioned processes, the catalyst must be maintained at a glowing temperature, which is accomplished solely by regulating the speed of the air alcohol mixture through the catalyst so that the reaction is suflicient to maintain the glowin condition of the catalyst. It is obvious t at such a process has several disadvant es; first, the catalyst must be maintaine at the glowing) temperature in order to -secure an apprecia le conversion; second, the time of contact of the vapors and cata- 1 st must be extremely short in order to re uce the complete combustion of the ethyl e pyrogenetic decomposition of the ethyl alcohol and acetaldehyde. This compensatin of running conditions makes the control 0 the process very diflicult. Various parts of the catalyst must, of necessity,

. difier quite widely in temperature in a process controlled in such a manner.

By m rocess however which is distinctly erent, fundamentally, from the processes referred to above, I have been able to effect aconsiderable improvement in the yield of acetaldehyde. My process is one of pure'catalytic oxidation while Orlofls proc- .ess, as he and other investigators describe it, is primarily'one of dehydrogenation, involving the reaction o H.o ='cn,cHo+H,, the presence of the very slight amount of oxygen in the form of air serving primarily to cop the catalyst in an activecondition.

I practice my invention by passing a mixaction can be rapidly removed as formed. For example, the catalyst may be contained 1n metallic tubes of small cross section immersed in a temperature controlling bath. Other meansof satlsfying the above necessary conditlons of this particular example will be apparent to those versed in the art of temperature control. At a speed equivalent to a time of contact of the air alcohol mixture with the catalyst of 0.39. second, I have been able to obtain a production of parts of acetaldehyde. per 100 parts of ethyl alcohol charged through the system with a simultaneous production of 10 parts of acetic acid per 100 parts of ethyl alcohol charged, with a complete combustion of the ethyl alcohol of only 3.0% of the amount charged. No carbon monoxide, hydrogen or hydrocarbons could be detected in the exit gases. This production of acetaldehyde corresponds to a theoretical yield of 85%, based on the alcohol undergoing oxidation. The remaining ethyl alcohol passes through unchanged and is recoverable. By time of contact is meant the length of time a molecule of the gas mixture is permitted to remain in contact with the catalytic zone.

Thus by a radical modification of the previously described rocesses, I have been able "to obtain a much igher theoretical yield of acetaldehyde with no detectable pyrolytic decom osition of the ethyl alcohol or the forms acetaldehyde and with a very small percentage of the alcohol undergoing comp'lete combustion to carbon dioxide and water. Furthermore, the catalyst temperature is easily controlled, as the amount of heat liberated during the oxidation is extremely small, since there is no decomposition of the alcohol other than that going into acetaldehyde and the small amount of acetic acid. The enormous increase in the exotherm of the reaction, when the oxidation proceeds beyond the aldehyde stage, is easil understood from the, following calculat1ons-For every pound of ethyl alcohol undergoing conversion into acetaldehyde, 2299 British thermalunits are liberated, while for every pound oxidized to acetic acid 4500 British thermal units are evolved, and for every pound undergoing complete combustion 13,300 Britishthermal units; thus the advantageof keeping the. j complete combustion at a minimum is evident.

1,oae,9s2 av If such a large excess of air which I have found so efiicacious under 'the conditions which I employ, Were used in the previously described glowing catalyst processes, substantially all the alcohol would undergo -combustion to carbon dioxide and water.

However, at the low catalyst temperature which I use, this excess of air is very .beneficial, as I am able to secure .a very high theoretical yield of aldehyde and a negligible loss of alcohol in the form of complete combustion.

I have tried other oxides including those of uranium, copper, chromium, manganese, cobalt, nickel, tin, thorium, zirconium, titanium, cerium, bismuth, molybdenum, tungsten, tantalum and others, in a manner exactly similar to that described above for vanadium oxide except that some temperature variations were employed in order to obtain the optimum production of acetaldehyde with each catalyst. Of these oxides investigated, I have found that cobalt oxide, tin oxide, cerium oxide and titanium oxide gave only traces of acetaldehyde, while the remaining oxides gave fair acetaldehyde productions which, however, were relatively small When compared with that resulting from vanadium oxide, and of these latter oxides chromium oxide, manganese oxide, uranium oxide and copper oxide gave, in addition to the aldehyde production, relatively high complete combustions of the ethyl alcohol.

I have found, however, that when mixtures are made ofsome'of these various oxides, which I have enumerated above, and are used as catalysts in the oxidation of ethyl alcohol to acetaldehyde, even higher yields of the latter are obtained than was possible with vanadium oxide, and in addition, other decided advantages are obtained with these mixed catalysts.

I have investigated a number of these mixed oxide-catalysts containing the oxides of at least two metals and have found that the metallic oxide components in such mixed catalysts exert a profound and unexpected influence on each other.

For example, I have found that small amounts of molybdenumoxide, when added to uranium oxide, give a catalyst which produces only acetaldehyde, there being practically no complete combustion and only a very small amount of acetic acid. In this mixture it appears as though the molybdenum oxide, which is fairly inert toward ethyl alcohol, except at high temperatures at which high complete combustionis obtained, functions in a way to depress the activity of the uranium oxide, the normal activity of which tends to exert itself largely beyond the ac- Likewise, an investigation of vanadium oxide-molybdenum oxide mixtures showedv that a mixture containing 5% of molybdenum (side was more satisfactory than a straight vanadium oxide catalyst.

I have also investigated numbers of ternary mixtures and have found that of the uranium oxide, copper oxide molybdenum oxide mixtures, a mixture of approximately 87% uranium oxide, 5% of copper oxide and 8% of molybdenum oxide gave a very high aldehyde production with practically no accompanying acetic acid production .or complete combustion. The proportions of oxides in another ternary -mixture which I have found to be quite successful, as far as the acetaldehyde production is concerned, consists of uranium oxide, 6% vanadium oxide and 9% molybdenum oxide, but with this mixture a small complete combustion of alcohol was observed with a very small acetic acid production.

Although several mixed catalysts have .thus been described, it is the intention not to be limited to the proportions in these specific all should catalyze the oxidation of eth l alcohol to acetaldehyde, as for examp e, those oxides which I have previously mentioned as giving small acetaldehyde produc-. tions when used alone.

In the preparation of these mixed catalysts it is preferable that the component metallic oxides should be in the most minutely divided state possible and in intimate contact with each other in order to secure the maximum benefit of the mixed catalyst.

The production of these mixed catalysts can be accomplished by starting with a solii tion containing the salts of the metals, the oxides of which metals are desired in the finished catalysts and which metallic salts, on ignition, leave only the oxides of the metals, or it is also possible to use a water suspension of the oxidesor hydroxides of the metals. However, I have achieved the greatest success by employing a solution of the complex organic acid compounds of the metals, as described in my co-pending applicatlon, Serial No. 513,111. The carrier, which may consist of crushed pumice or other suitable powdered, granulated or' fibrous material, which is chemically inactive and acts merely as a mechanical distributor, may then be added to the prepared solution or water suspension of the metallic tions enumerated above in order to utilize compounds and the whole evaporated to dryto the greatest advantage the improvement ness whilebeing stirred, after which it is in the compositionof the catalyst. Considignited'inair or other gas orin the presence erable variation also exists in the temperaof the gas mixture containing ethyl alcohol ture of the catalyst mass, which temperature and oxygen to be employed in the catalysis. will be influenced by variations in the condi- My invention will be further-explained in tions previously mentioned, but in all cases I connection' with the following example the temperature must be maintained below which is given for illustrative purposes. It the point at which pyrolytic decomposition is intended not to limitthe procedure to the of the ethyl-alcohol or the generated acetalexact detailsgiven, as the process can be dehyde ensues. I have found that the catavaried over wide limits both in the choice lyst temperature should not exceed 500 C. of the conditions and also in the composition. Thus, by means of processes diflering radiof the catalyst, without departing from the cally-from the previously described processes spirit and scope of the invention. for obtaining acetaldehyde from ethyl alco- Amixture of approximately 14 parts of hol, which processes inc ude a relativel low air to 1.0 part of ethyl alcohol by weight is reaction temperature, a great excess 0 oxypassed through a. catalyst consisting of gen over the theoretical requirement, and a crushed pumice impregnated with a mixture diflferent type of catalyst, I have been able to of 93% 'of uranium oxide and 7% molybobtain greatly augmented productions of denum oxide held-at a temperature of about ac'etaldehyde with very small acetic acid 375 0., measured by inserting a thermoproductions and practically no complete couple directly into the catalyst mass and combustion of th thyl l ohol h n ompassed through cru b Collected ill has been observed. The absence ofcomp maintaining a time of contact of the aired with reviou ly de ribed rocesses, alcohol mixture with the catalyst of 0:38 In theoretical yields I haverbeen a le to apsecond. The catalyst mass may e m proach close to 100%. Furthermore, my oxitained at the desired tempera u as dation process'is always conducted at such scribed above. The products of the react on, l t m t (b 1 '5009 0, t l t together with the small amounts of untemperature) that no detectable pyrolytic dechanged alcohol, may then be condensed composition of ethyl alcohol or acetaldehyde etc Some other n the acetaldehydfl combustion-of the ethyl alcohol and the very COVGIBCI, and the unaltered 8.1001101 regained small acetic acid production causes such a and used over again. v small exotherm that t e catalyst temperature product-ion Of '57 pounds 0f acetaldecan be and curately controlled,

hyde per pounds of ethyl a h charged which condition is so essential to the success ,a simultaneous acetic acid through the System was Obtained-along with of a catalytic oxidation process. Another l'oductlon of advantage of my process is that relatively Pounds P 100 Pounds of a cohol g d impure alcohol can be employed with satisand with no complete combustion. This f t 1t 4 yieldof acetaldehy e corresponds to a theore'tical yield of 93%, i, e. based on the alcohol I claim 1. The process of producin acetaldehyde,

' undergoing oxidation, and leaves about 40% hi h mprises passing ethy alcoholin the v tions of the reactionas stated above are caof the charged alcohol which passed through vapor phase and an oxygen-containing gas unchanged to be subsequently recovered. i t t t ith di id t t It will be evident that the various cond1- pemtum f b t 300 C, v v 2. The process of producing acetaldehyde, Pablo of wide v a g these which'comprises' passing ethyl alcohol in the 'ditions may be mentioned th p re vapor phase and an oxygen-containing gas which the oxidation is carried out, as for'exvi t t t with a di o id at g ample, thereaction may be conducted at atrature of about 300. C.- ior approximately .mospheric pressure or at increased 01' di- 0,4 f e nd. mimshed pressure; the time of contact of the 3, Th'process of producin acetaldehyde,

tion of catalyst to the reaction gases" the vapor phase and an oxygen-containi relative proport 0 e hyl-alcoho oxyinto contact with a catal st comp o:

gen-contaimng ga w h m y n f ides of two inetals oft e fifth and sixth Ill reaction gases with thecatalyst; the pr0p which comprises passing ethy alcohol in the oxy' n, or ozone, or almixture of any orall periodic groups for aboutOAof aheeond at.

of t see or other gases which contain free a temperature below500 C. oxygen. These conditions are all more or 4. The process of produci acetaldehyde, -less dependenton each other. Furthermore, whichcomprises passing ethyl alcohol in the much variationvexists in the choice of the vapor phase and an oxygen-containing gas catalyst, hich in=turn will tate into contact with a catalyst comprising 0:- variation or'adjustment of the other condiides of vanadium and molybdenum, I v

5. The process of producing acetaldehyde which comprises passing ethyl alcohol in the which comprises passing ethyl alcohol in the vapor phase and an oxygen containing gas vapor phase and air in approximately the into contact with vanadium oxide at a tem- I proportions of 1 to 14 into contact with perature below 500 0.

5 vanmgum oxide at a temperature of about In testimony whereof I afiix my signa- 300 ture.

6. The process of producing acetaldehyde AUGUSTUS E. CRAVER. 

